Self-adjusting tappet



Dec. 23, 1930. R. H. HAMILTON SELF ADJUSTING TAPPET Filed Jan. 9, 1930 #hm RNEYS Patented Dec. 23, 1930 UNITED STATES PATENT- OFFICE -SELF-ADJUSTING TAPPET W ZEALAND UED Application led January 9, 1930, Serial No. 419,511, and in New Zealand November 1, 1929.

This invention relates to tappets by means of which intermittent one-way thrust motion is communicated from a driving to a v driven part, such for .example as the tappets Ulemployed between the cam-shaft and the poppet-valves of an engine.

It is well recognized that, to operate efficiently, tappets of this kind must be of the exact length to fit between the said driving i@ and driven parts, with an allowable clearance, as in cases where a tappet is too short a certain amount of movement is lost and excessive wear and noise result, while in the event of the tappet being too long the driven part is not permitted t0 fully return or reseat during the intervals between successive thrust impulses.

To maintain them in efficient condition therefore tappets require adjustment from time to, time to compensate for wear that must inevitably occur in working surfaces.

It is the object of the present invention however to provide a tappet of novel and peculiar construction whereby the necessary,v 25 adjustment of its length will occur automatically while the same is in use.

In addition to its value in saving manual adjustment and promptly compensating for any wear, or stretching, that may occur in its co=operating parts, the present invention possesses the further advantage that it automatically adjusts itselt` to compensate for slight variations that may occur in the spacing of the driving and driven parts due to temporary expansion ,andcontraction of the metal ring in response to endwise impulses upon suph members, one of the internal threads and its received external thread being right-handed while the other internal j and external threads are left-handed.

In order that the nature of the invention and its construction may be clearly understood, it will now be fully described and explained with reference ,to the accompanying drawings, in which Fig. 1 isan elevation of a tappet in accord- 55 the tappet and its co-operating parts in more or less diagrammatic form illustrating its self-adjusting functions.

For the sake of illustrating its function, the tappet is hereshown as communicating the thrust action of a cam l to the stem 2 of a valve operating against a valve-spring 3 in accordance with the well known practice in internal-combustion engines.

The tappet is however equally adapted for use in other forms of mechanism in which an intermittent one way thrust between a driving and a driven part is required.

In construction the tappet comprises al sleeve 4 having an internal thread to receive a corresponding external thread 6 upon an intermediate member 7 which latter is formed also with an internally threaded axial bore 8 to receive a corresponding external thread 9 upon a third member 10.

One extremity, 11 of the said intermediate member 7 at one end of the sleeve 4: constitutes one operative end of the tappet the other operative end of which is constituted by a head 12. upon the third member 10 at the other or opposite end of the sleeve 4.

The said threads are of sufficient coarseness to permit of the parts being screwed one within the other in response to impulses applied end-wiseto lsuc-h members and one pair of such threads is formed in the opposite direction to the other pair.-

Thus, as here shown, the threads 5 and 6 10o may be left-handed while the threads s mi 9 are right handed.

The third member 10 has a tendency to unscrew itself from the intermediate member 7; thereby placing its head 12 at an interval from the adjacent end of the sleeve 4, for a purpose hereinafter explained, such tendency being preferably attained by the provision of a spring.

In the preferred form of the construction this spring 13 is of the torsion type anchored at one end to the sleeve 4, while its other end is attached to some part of the third member 10, as by inserting itin a hole in the head 12 of such member, as here shown, such spring being arranged to act axially upon the member 10 in the unscrewing direction, as here shown. The said torsion spring is preferably arranged also to act slightly in tension between its said connected parts.

Although other types of springs may be employed for this purpose a torsion-spring acting between the third-member 10 and the sleeve 4 as here shown possesses the very important advantage that, iii' addition to imparting the required tendency' to the third member 10, it serves also to keep all the threads in the correct bearing relation for the operative action hereinafter explained, thereby avoiding any lost motion that might otherwisc occur in consequences Aof looseness in the threads due to wear or other causes.

The head 1 2 of the third member 10 is adapted to come in Contact with and friction ally engage its adjacent end of the sleeve 4, for which purpose such head is preferably formed with a tapered formation 14 adapted to receive a corresponding tapered formation 15 upon the said end of the sleeve.

The tappet thus constituted is arranged as here shown, its end 11 being operable upon the drive-n part 2 and the head 12 being acted upon and under constant control by the driving part 1.

1f thought necessary or desirable also a piece of fibre or other suitable substance may be inserted in a recess in the end 11 to receive the contact with the driven part 2 and thus reduce noise.

The sleeve 4 is mounted to be capable of longitudinal reciprocation between such driving and driven parts, as for example by arranging it to slideA within a tappet guide 16. The ,said sleeve may, when necessary, be restrained from axial turning by any suitable means. such for example as by the provision in the tappet-guide 16 of a feather 17 received in a feather-way 18 in the sleeve. However, when a torsion spring is used, this provision is unnecessary. Provision is made also for limiting the said movement of the sleeve 4 towards the driving part 1, as for instance b v the provision upo'n the sleeve of an outturned iange 19 adapted to come in Contact with the end of the tappet-guide 16 adjacent to the driven part.

The arrangement shown in Fig. 3 is identical with that already described with the addition of a second sleeve 20 having a closed end and arranged to slidably receive the sleeve 4 and head l2.

In this case the said sleeve 20 is itself slidably received in the tappet-guide 16 and the necessary restraint of the sleeve 4 against axial turning is accomplished in any suitable manner, as by the provision in the sleeve 2O of a feather-way 21 to receive the aforementioned feather 17 in the tappet-guide and the provision in the sleeve 20 of a feather 22 to be received in the feather-way 18 of the sleeve 4.

In this case the driving part 1 acts upon the head 12 through the medium of the said closed end of the sleeve 2O and such end is preferably arranged to frictioiially engage the head for which purpose the latter is preferably formed with a tapered formation 23 to be received vby a corresponding tapered formation 24 in the said end.

The operation is brieiiy as follows When the tappet comes to its position of rest in the intervals between successive operative impulses from the driving part l to the driven part 2, its sleeve 4 is arrested at a predetermined limit of proximity to the driv ing part 1 by its said stop means, constituted as by the contact of the flange 19 with the end ofthe tappet guide 16.

This arresting of the sleeve is arranged to take place slightly before the return of the driving part 1 is fully completed and consequently during the remainder of such return movement the third member 10, owing to its aforementioned tendency, unscrews itself slightly from the intermediate member 7, thus placing its head 12 at an interval from the end of the sleeve, as shown in Figs. 1, 3 and 4, and in which condition the said threaded members are capable of movement in relation to one another.

W'hen the parts are in this condition the third member 10 possesses somewhat greater resistance to movement into the intermediate member 7 than does the latter to movement through the sleeve 4l..

When therefore the driving part 1, in commencing its operative movement, applies a thrust to the head 12 the third member 1() and intermediate member 7 attempt to move through the sleeve towards the driven mem ber.

If the tappet is of the correct length as in Figs. 1 and 3, this movement'will be frustrated b v reason of the fact that the end 11 of the intermediate member is already in contact with ythe driven part 2. Should the tappet be too short however, as in Fig. 4, this moi-ement of the members 10 and 7 will actually take place until the said end 11 contacts with the driven part, as shown in Fig. 5, thereby producing the required lengthening of the tappet.

In the event of the deficiency inthe length of the tappet being too great to allow of its beving fully made up in a single movement as above explained, the adjustment will occur progressively as the result of two vor more successive movements.

Vhere, however, a torsion spring is employed to act between the sleeve 4 and the third member 10 as described, such spring will exert a constant control upon the inter- `mediate member 7 tending to keep the end 11 of the latter in contact with the driven lpart 1.

ment of the driving part 1, as previously explained.

In either case however the intermediate member 7 being thus arrested'bycontact with the driven part 2 the subsequent movement of the driving part'l causes the third member 10 to move into the intermediate member 'i' until the head 12 comes in contact and frictionally engages the end of the sleeve 4, thus locking both pairs of threads and so rendering the tappet rigid to slide through the guide and so convey the operative movement from the driving part 1' to the driven part 2, as shown in Fig. 6. y

In the event of the tappet being too long the driven part 2 will not be returned or seated when the sleeve 4 is arrested by contact of its flange 19 with the end of the tappet-guide. Upon the sleeve being arrested and the head 12 disengaging the sleeve 4 therefore the pressure of the driven part 2 upon the end 11 forces the intermediate member into the sleeve until such driven member reaches its fully seated position.

In the case of the construction shown in Fig. 3, the functions of the tappet in lengthening or shortening to accommodate itself to the driving and driven lparts will be identical with that already described. In this case however the friction of the sleeve 2Q with the head tends to reduce the freedom of the latter to axial turning and so serves to stabilize the action of the third member 10.

In addition to this the interior of the sleeve 20 serves as an oil-container, thus ensuring a thorough lubrication of the internal parts of the tappet independently of other sources.

Again in cases where the tapnet is to be provided with an anti-friction roller or other special formation to be received by the driving part 1, the said sleeve 20 affords a convenient means whereon such roller or formation maybe mounted and serves also as a guide by means of which the third member 10 is relieved of lateral strain.

The slight interval that must necessarily occur between the head 12 and the end of the sleeve 4 when the tappet occupies its position of rest need be no greater and may indeed be even less than the customary clearance allowed between a tappet of the ordinary kind and the driven part, say one or more thousandths of an inch, and consequently the self adjustment provided by a tappet in accordance with this invention will be as correct and accurate as would be possible with manually adjustedtappets.v Again the ability to automatic re-adjustment after each operative movement enables a tappet in accordance with the present invention to compensate not only for the gradual effect of wear, but also for temporary changes in t-he spacing of the'driving and driven parts due to expansion and contraction of metals in consequence of temperature variations, or other causes.

I claim:

1. A tappet comprising a sleeve reciprocable longitudinally between a driving and a driven part, an internal thread in said sleeve, an intermediate member havingone end actable upon said driven part, said member being formed with an external thread received in said thread in the sleeve, an axial bore in said intermediate member having an internal thread formed in the opposite direction to that of aforesaid threads, a third member having an external thread .received in said threaded bore, all of said threads being of sufficient coarseness to permit of said members being screwed one within the other in response to endwise impulses, a head upon said third member actable upon by said driving part and adapted under pressure of the latter to, contact with the adjacent end of said sleeve, thereby to retain said threaded parts rigid, stop-means limiting aforesaid movement of said sleeve towards the driving part, and meanstending to unscrew said third member from said intermediate member thereby to carry said head clear ofthe sleeve to permit of said threaded members re-adjusting themselves to the requirements of said driving and driven parts when said sleeve is in contact with said limiting stop.

l2. A tappet comprising a sleeve reciprocable longitudinally between a driving and a driven part but restrained from axial turn# tion 'to that of aforesaid threads, a third member having an external thread received in said threaded bore, all of said threads being of suflicient coarseness to permit of said members being screwed one within the other in response to endwise impulses, a head upon said third member actable upon by said driving part and adapted under pressure of the latter to contact with the adjacent end of the sleeve thereby to retain said threaded parts rigid, stop-means limiting aforesaid movement of the sleeve towards said driving part, and a spring tending to unscrew said third member from said intermediate member thereby to carry said head clear of the sleeve to permit of said threaded members re-adj usting themselves to the requirements ot said driving and driven parts when said sleeve is in contact with said limiting stop.

3. A tappet comprising a sleeve reciprocable longitudinally between a driving and a driven part but restrained from axial turning, an internal thread in said sleeve, an intermediate member having one end actable upon said driven part, said member being formed with an external thread received in said thread in the sleeve, an axialbore in said intermediate member having an internal thread formed in the opposite direction to that of aforesaid threads, a third member having an external thread received in said threaded bore, all of said threads being of suicient coarseness to permit of said members being screwed one within the other in response to end-wise impulses, a head upon said third member actable upon by said driving part and adapted under pressure of the latter to contact with the adjacent end of said sleeve, thereby to retain said threaded parts rigid, stop-means limiting aforesaid movement of said sleeve towards the driving part, and a spring acting in torsion between said sleeve and said third member and tending to unscrew the latter from said intermediate member thereby to carry said head clear of said sleeve to permit of said threaded members re-adjusting themselves to the requirements of said driving and driven parts when said sleeve is in contact with said limiting stop.

4. A tappet as defined in claim l wherein said sleeve is slidable within a tappet guide and wherein said limiting stop is constituted by an out-turned ange upon said sleeve adapted to come in contact with the end of said tappet-guide `when said sleeve' reaches a predetermined position of proximity `to said driving part.

5. A tappet as defined in claim 1 wherein said head of the thirdpmember is provided with a tapered formation to receive a corresponding tapered formation upon the end of the sleeve.

6. A tappet as delined in claim 1 wherein sald sleeve is slidably but non-rotatably received within a second sleeve having a closed end to enclose the head of the third member and provide a medium whereby the latter is acted upon by said driving part.

'i'. A tappet, comprising an internally threaded outer sleeve reciprocable longitudinally between a driving member and a driven member, an externally threaded member disposed within and spaced from said sleeve. the thread ot' said member being formed in the opposite direction from that of the sleeve, said inner member having at one end a head disposed in position to be acted on by said driving member, an intermediate sleeve disposed between said outer sleeve and the inner member and having exterior and interior threads engaging the threads of said sleeve and inner member respectively, said intermediate sleeve having means at one end there of for actuating the driven member, and means tending to unscrew said inner member from said intermediate sleeve.

In testimony whereof I have hereunto aiiixed my signature.

REGINALD HAROLD HAMILTON. 

